David stoddart



NAPETERS, PHOTOLLITKOGRAPMER, wASHlNGTON, D. C.

geiten tetes tttwt @fitta `DAVID s'roDDAnT, oFsANfFnANoIsCo, CALIFORNIA.

@tige Sflgchuie rentra in iii that inlets ttmt mit mating part nt tige tante,

TO ALLv WHOM ITMAY CONGERN:

Be it known that I, DAVID STODDAM, of the city aud county of San Francisco, and State of California, have invented certain Improvements invDirect-'Acting Steam-Engines; and I do hereby declare t'hat the following is a full and exact description, reference being had to the accompanying drawings, and to the letters of. refercncemarked thereon, said drawings forming a part of this specicatio i Figure 1 is a' vertical section through the axis of -the steam-cylinder,

Figure 2is one-half plan', and

Figure 3 is o. vertical cross-section through the centre of steam-chest. d

A is a steam-cylinder; Bl-Bz are two pistons, connected together by the piston-rod; C is a slide-valve; D D2 are two small pistons, connected to'the slide-valve; E E2 are the steam-ports, and F is the exhaust-port,

opening intothe cylinder between the pistons B B2.v G is the opening for the exhaust-pipe. H1 H2 are two small passages, drilled into the cylinder and steam-chest, so as to connect the spaces behind the small pistons to the steam-cylinder. The steam-chest is set transversely to theaxisof the cylinder. Kl K2`arc two auxiliary passages, similar toHl H2, but connecting to the cylinder at di'erent places. L L2 are partitions, separating thesmall 'piston-chambers from the steam-chest, and through which pass the piston-stems, and alsoa small hole through each to admit eteam- Thcse partitions serve as abutments to check the throwof the main valve, and, by the compression of steam between them and the small pistons, an elastic cushion is formed, which obviates any injurious percussion.

The drawings show the engineias in motion, in the direction of the arrows Ml M2, but at the instant when -the change of direction is about to take place. `'.lhe arrows in the various passages show the direction of the .currents of live and exhaust steam at the instant before the change of the valve to reverse the stroke.

l The action is thus: .The slide-valve being in the position in iig. 3, steam is admitted behind main piston Bl, producingimotion until opening Hl is passed, then the steam from the cylinder rushes to the space behind small piston Dl, and reverses the valve, thus admitting steam behind the other main piston B2, which produces motion in the reverse direction until opening H2 is' passed, when the steam-rushes tothe space behind small piston D2,

and again changes the valve to the original position. The-steam from behind D1 and D2 .exhausts back again into the cylinder through the ysame passages Hx and H2, and the main pistons' Bl B2 are set lso-far apart that neither can ever entirely blank the main exhaust,or pass more than one opening Hll or H2. The passages K1 K2, shown by dot-ted lines, are auxiliary, and used for the purpose ofpreventing a. change of valve While the piston is passing across the ,opening H1 or H2. For ifeither of the small pistons Dl or- D2 should leak,` then the pressure behind it might accumulate, while the main piston is passing its connecting-passage, and throw the valve before 4the proper time, particularly if the engine is working at a slow speed. I But theopenings KK2, con-.

nesting the spaces behind D D2 to the cylinder, as represented, keep a. communication operi' to the exhaust up "to the lust instant, for the main piston will just blank the second opening'K1 or K2 as it opens the irst, Hl or H2.

This is' an important feature, as a. liberal depth of piston may thus be used, and also a slow speed of engine,- when required, without affecting tbe'length of the'engine-strolie.l i

The steam-chest is set transversely, because the main steam-ports andlpassages I-I1 H2 are more direct than when the stenmhest-is in line with the cylinder, and for the further reason that the engine may be used 'inupright' position without theaction of gravity interfering with the motion'of the valve-andpistons Dl D2. It is not new to control steam-valves by steam derived from the cylinder, but in the arrangements heretofore usedvit is customary to permit the main piston to pass both openings corresponding to Hl H2, but in'myl invention thev general arrangement never permits bothof .those passages to be closed from the exhaust at one time. Thus I am enabled to produce u positive motion,- either slow or fast, and also to obviate-'any pernicious effects of either natural, or undue leakage of any of the pistons or valve.

I-claim the arrangement ofthe pistons B132, small pistons D D2, valve C, andthe. passages Hl H2, bom'- municaiting to the cylinder, substantial-lyas described. y

2. I claim the arrangement of the auxiliary passages' K1 K2, substantially Ias described.

` DAVID s troDDART. Witnesses DAVID RUTHERFORD, JULIUs A. PORTER. 

